Inherited a Street Beast from my dad

[cycleguy55]

I have 3.00:1 behind my 460 and they work fine with my transmission. Combined with the 3.28:1 first gear ratio, I have a combined ratio of 9.84:1 and it will launch pretty well. With my tire size of 295/50R15 (overall diameter of 26.6"), I'm running 2,650 RPM @ 70 MPH.

Your choice of rear end ratio will depend upon the overall ratios - 1st gear as well as top gear. As this is primarily a street car, how much highway or freeway use do you expect?

The first thing is probably to determine exactly what you have in both rear end (count the teeth) as well as transmission. How tall are your rear tires going to be? What is the maximum RPM you expect to run? Once you have that information you can go to any one of many gear ratio calculators, plug in your ratios and see whether that will work for your intended usage. The one at Calculators is pretty good, but there are plenty of other online calculators.

[Tom Wells]

ziggy75,

It depends

But you knew that...

First, what transmission do you have or plan to use?

I use C-6 automatics which have a 1:1 ratio in third. I use 2.73 8.8 rears and am very happy with the results.

If you have or intend to use an overdrive trans, you may want a higher number axle, say 3.55 or 3.73

To find out what ratio is installed in the rear you have, count the ring gear teeth (the large one with the big hole in the middle) and the pinion gear teeth (much smaller with no hole). Then divide the ring gear count by the pinion count. An example is: ring gear 41, pinion 15, so 41/15 = 2.73333 which is called a 2.73

Hope this helps,

Tom

[ziggy75]

I believe its a C6. It is what came with the 69 Lincoln. As stated earlier, the carrier is still in the axle but I plan on switching out the carrier with a 31 spline Explorer carrier. The axle that he bought ended up having a broken axle, which he didnt realize until after we got it home. He wasnt too happy about that. I have a set of 17" Cobra R rims. So I am thinking 245/45-17's.

As for replacing bearings and such, should I purchase the $110 kit and do everything? I would hate to go through it all if it doesnt really need it.

[Tom Wells]

ziggy75,

Hmmm....

Rebuilding a differential is not a beginner's chore. The pinion depth needs to be exact, and the tooth engagement pattern takes some labor to get correct.

Here's a sample of "how-to": 1998 Ford Mustang Cobra Budget Rearend Rebuild - MM&FF

The fancy limited slip isn't needed for normal street use; you can use the standard one from Ford perfectly well.

If you search on "mustang 8.8 axle rebuild" you'll see a bunch of hits describing how other folks get it done.

Then, you decide. Is it better to have a pro do this job? I can't answer that one for you - I have done a couple and they didn't always turn out perfect - perhaps yours will!

If it was easy, someone would have already done it LOL

Tom